Biological circuit components created by scientists
1 min read
In a move that could pave the way for direct biological integration into electronic circuits, researchers from the University of Pennsylvania have formed biological molecules connected to electrodes, as well as a new microscope technique for measuring them.
Led by Dawn Bonnell, director of the Unviersity's Nano/Bio Interface Center, the team arranged artificial proteins, bundles of peptide helices with a photoactive molecule inside, on to electrodes. When light hit the proteins, they converted photons into electrons and passed them to the electrode. "It's a similar mechanism to what happens when plants absorb light," explained Bonnell, "except in this case, we wanted to use the electron in electrical circuits."
Because electrical properties of a large chunk of a single element can be measured and scaled down, but not scaled up, the researchers decided to invent a new way of measuring them. They also set out to find a controlled way of making the photovoltaic proteins that would resemble how they might eventually be incorporated into devices in open air.
To do this, they invented a new kind of atomic force microscope technique, known as torsional resonance nanoimpedance microscopy. "Atomic force microscopes operate by bringing an extremely narrow silicon tip very close to a surface and measuring how the tip reacts, providing a spatial sensitivity of a few nanometres down to individual atoms," said Bonnell. ""In our version, we used a metallic tip and put an oscillating electric field on it."
By seeing how the electrons reacted to the field, the team was able to measure more complex interactions and properties, such as capacitance. The researchers designed the self assembling proteins much as they had done before but took the additional step of stamping them onto sheets of graphite electrodes. They believe this manufacturing principle and the ability to measure the resulting devices has the potential to be used in a variety of applications.
"Photovoltaics and solar cells are perhaps the easiest applications to imagine," maintained Bonnell, "but where this work is going in the shorter term is biochemical sensors. Instead of reacting to photons, proteins could be designed to produce a charge when in the presence of certain toxins, either changing colour or acting as a circuit element in a human scale gadget."
